struct _item {
	struct _item * left;
	struct _item * right;
	int data;
};

typedef struct _item item;

struct _tree {
	item *root;
	item *pre;
};

typedef struct _tree tree;

tree * init_tree(tree * wtree, int data);
tree * insert_tree(tree * wtree, int data);
tree * delete_tree(tree * wtree, int data);
tree * find_tree(tree * wtree, int data);
